KR20190096361A - Method for improving wettability of surface of solid substrate by liquid metal - Google Patents

Abstract

The present invention is a method of processing a solid substrate made from a first metal of metal or ceramic type, the method comprising placing a substrate in contact with a liquid metal while the substrate is exposed to an ultrasonic wave called a power wave. Steps. At the surface level of the substrate, the power density is greater than the cavitation threshold of the liquid metal. This exposure improves the wettability of the substrate surface by the liquid metal.

Description

Method for improving wettability of surface of solid substrate by liquid metal

The technical field of the present invention is the alteration of the wettability of the material surface to the liquid metal under the influence of exposure to high power ultrasound.

In some applications, it is necessary to form a metal layer, known as a coating metal, on the substrate. This is the case, for example, when aluminum wire is intended to be used as an electrical conductor. The low mass of this wire makes the wire particularly suitable for automotive or aviation applications. Because of the formation of an insulating oxide layer on the surface, aluminum wire has a high surface resistance, which is disadvantageous for obtaining a good electrical connection. When the wire has a large cross sectional area, coating with a nickel layer is described in patent FR2796656. The method of this patent works for wires close to 0.5 cm in diameter, but because it is too slow, it is not satisfactory for smaller diameter wires, for example 0.2 mm. In order to improve the adhesion of tin or tungsten type coating metals on aluminum wires, chemical surface treatments and electrochemical surface treatments have been developed.

We have demonstrated that other methods can be used to obtain good adhesion of the liquid coating metal onto a substrate, for example an aluminum substrate. They have shown that the wettability of a substrate can be increased by a physical process that is simple to use and compatible with industrial applications. In addition, they have found that the increase in wettability can be utilized in other applications, in addition to applying a metal coating on a substrate.

One object of the present invention,

a) bringing the solid substrate into contact with the liquid metal confined within the enclosure;

b) propagating an ultrasonic wave, called a power wave, emitted by a power ultrasonic generation device in the liquid metal, wherein at the surface of the solid substrate, the power density of the ultrasonic power wave is a liquid metal. The ultrasonic power wave propagates through the liquid metal before reaching the surface of the solid substrate, such that the frequency of the ultrasonic power wave is between 10 kHz and 250 kHz so as to be greater than a cavitation threshold of.

c) after propagation of the ultrasonic power wave, obtaining a cavitation bubble in the liquid metal, wherein the cavitation bubble reaches the surface of the solid substrate and the interaction of the surface of the solid substrate with the cavitation bubble is caused by the liquid metal. Increasing the wettability of the surface

It is a method of processing a solid substrate, including.

The cavitation threshold refers to the power density of ultrasonic power waves in which cavitation bubbles are formed in the liquid metal when this threshold is exceeded. This may be a volume power density or a surface power density. In general, during step b), the surface power density is greater than 1 W / cm ² or even 5 or 10 W / cm ² .

The solid substrate is formed of a first metal whose melting temperature is higher than the melting temperature of the liquid metal.

According to a preferred embodiment, the frequency of the ultrasonic power wave is greater than 40 kHz, preferably 40 kHz to 80 kHz. This makes it possible to increase the wettability of the surface of the solid substrate by the liquid metal without damaging the surface state of the solid substrate.

Advantageously, during step c), the acoustic power wave propagates within the enclosure, in a liquid metal, at a propagation distance of greater than 1 cm, preferably greater than 5 cm.

Ultrasonic power waves can propagate, in particular, from a power generator and pass through a so-called interface that extends in contact with the liquid metal, which method utilizes cavitation bubbles inside a cone 15 called a hyper-cavitation cone. Forming a cavitation bubble, wherein the density of the cavitation bubbles is greater than at the outside of the cone, the hyper cavitation cone extends from the interface within the liquid metal, and in step c) the solid substrate is arranged outside the hyper cavitation cone To make it happen. In particular, the interface may be a solid wall on which ultrasonic power waves propagate. This may be part of a wall of the enclosure or a wall defining a waveguide through which acoustic power waves propagate.

According to one embodiment, the solid substrate may be a metal or ceramic substrate, the method further comprising the following additional steps, namely

d) exposing the substrate to ultrasonic power waves, preferably during an exposure period of 1 second to 1 minute, wherein the liquid metal forms a layer known as a coating layer on the substrate;

e) removing the substrate from the enclosure;

f) after removal, solidifying the liquid metal to form a deposit on the substrate

It includes.

According to this embodiment, the substrate may be metallic, and the metal comprises a substrate having a melting temperature that is strictly greater than the melting temperature of the liquid metal. The liquid metal may be an electrically conductive metal such that the deposit formed in step f) is an electrically conductive deposit. The liquid metal may especially contain tin, zinc or lead. The thickness of the deposit formed during step f) is preferably between 5 μm and 2 mm.

According to one embodiment, the liquid metal comprises aluminum. It may then comprise a mass fraction of magnesium, preferably less than 1%.

According to one embodiment,

The ultrasonic control device propagates an ultrasonic wave called a control wave in the liquid metal through a surface known as a coupling surface, the coupling surface being the surface of the solid substrate extending in contact with the liquid metal;

The solid substrate is delimited by the coupling surface,

During step c), the wettability of the surface of the solid substrate by the liquid metal is increased in the liquid metal to improve the transmission of the ultrasonic control wave through the coupling surface. The power density of the ultrasonic control waves in the liquid metal is generally below the cavitation threshold.

The ultrasonic control device may be disposed outside the enclosure, where the coupling surface corresponds to the interface between the enclosure and the liquid metal through which the ultrasonic control wave propagates, and the solid substrate is at a portion of the enclosure that is bounded by the coupling surface. Is formed by.

The ultrasonic control device may be confined within the containment system, the containment system is immersed in the liquid metal, the coupling surface corresponds to the interface of the containment system with the liquid metal through which the ultrasonic control wave propagates and the solid substrate is coupled to the coupling system. It is formed by a portion of the containment system that is delimited by the surface.

According to one embodiment, the chamber may be a reactor vessel, and the liquid metal contains sodium or lead.

Other advantages and features will become more apparent from the following description of specific examples of the invention, which is provided by non-limiting examples and shown in the figures enumerated below.

1A shows a first embodiment of the present invention. 1B shows a second embodiment of the present invention. FIG. 1C shows the detail of FIG. 1A. FIG. 1D shows the detail of FIG. 1B.
2A and 2B show cross-sectional views of aluminum alloy wires immersed in a bath of liquid tin without using the present invention, and cross-sectional views of aluminum alloy wires immersed in a bath of liquid tin using the present invention, respectively. . FIG. 2C is a detailed view of FIG. 2B. 2D and 2E show longitudinal cross-sectional views of an aluminum alloy wire immersed in a plating bath of liquid tin using the present invention. FIG. 2E is a detail of FIG. 2D.
Figure 3a is a cross-sectional view of a cross section of the aluminum wire to which the method according to the present invention is applied. FIG. 3B shows the detail of FIG. 3A. 3C, 3D, 3E and 3F are X-ray fluorescence spectra corresponding to different analysis points in FIG. 3B.
Figure 4a is a scanning electron microscope to observe the longitudinal section of the aluminum wire to which the method according to the invention is applied. 4B shows the details of FIG. 4A. 4C, 4D, 4E and 4F are X-ray fluorescence spectra corresponding to different analysis points in FIG. 4B.
Figure 5a is a cross-sectional view of an aluminum wire to which the method according to the present invention is applied with a scanning electron microscope. 5B and 5C show the two regions of interest of FIG. 5A. 5D, 5E and 5F are X-ray fluorescence spectra corresponding to different analysis points in FIG. 5B. 5G and 5H are X-ray fluorescence spectra corresponding to different analysis points in FIG. 5C.
6A and 6B are examples of use of the invention in accordance with a first application for forming a metal deposit on a substrate.
7a and 7c schematically show two uses of the invention according to a second application for nondestructive testing of a reactor vessel. 7B and 7D are detailed views of FIGS. 7A and 7C, respectively.

The use of ultrasound is common in a variety of industrial applications. Ultrasound can be used at high power, for example, for application in cleaning applications. In general, ultrasonic waves are used at low power for applications in nondestructive testing applications in materials and structures.

The present invention is based on the beneficial use of power ultrasound to increase the surface wettability of solid substrates by liquid metal. The inventors have found that applying high power ultrasound to a metal or ceramic substrate immersed in a bath formed by liquid metal increases the wettability of the substrate surface by the liquid metal.

According to a first application, the invention is used to deposit a metal layer on a substrate. A first embodiment is shown in FIG. 1A. The solid substrate 21 formed by the first material, for example, aluminum alloy or ceramic, is immersed in the plating bath of the second metal 22 in the liquid state. In this example, the liquid metal is tin. The liquid metal plating bath is included in the crucible forming the enclosure 20. In this example, the mass of the liquid metal 22 is 5 kg, and the metal bath is heated to a temperature of 350 ° C. The melting temperature of the liquid metal should be strictly below the melting temperature of the first material forming the substrate.

An ultrasonic generator device 10, known as a power generator (or ultrasonic motor), is disposed near the enclosure 20, and a waveguide 12 extends between the ultrasonic generator 10 and the liquid metal plating bath 22. The waveguide 12 is immersed into the liquid metal 22 and allows the ultrasonic wave 11 emitted by the ultrasonic generator 10 to propagate in the liquid metal 22. The ultrasonic generator 10 is, for example, a piezoelectric transducer which can be deformed when subjected to alternating electrical polarization, which deformation generates an ultrasonic acoustic wave 11. The ultrasonic wave 11 propagates inside the waveguide 12. The waveguide may be formed of, for example, a metal based on titanium or a rigid ceramic.

The ultrasonic wave 11 emitted by the power generator 10 is a high power wave. High power means 10 W to 200 W or more, so the power density in the substrate 21 is greater than the cavitation threshold of the liquid metal 22. The cavitation threshold can be expressed according to the surface power density, in which case depending on the liquid metal 22 and the temperature, at least 1 W / cm ² , or even at least 5 W / cm ² , or even more than 10 W / cm ^2. Can be larger. Further, preferably, the power of the ultrasonic wave 11 is adjusted to obtain a surface power density greater than the cavitation threshold of the liquid metal 22 for all or part of the surface of the solid substrate.

The appearance of cavitation in the liquid medium generates acoustic waves, and the detection of the acoustic waves makes it possible to detect the occurrence of the cavitation. Cavitation thresholds in liquid metal can be determined experimentally by methods based on the detection of such acoustic waves. Examples are provided in the documents FR2404850 and EP0221796. In addition, an optical cavitation detection method is described in WO2006034040.

The inventors have discovered that the formation and propagation of cavitation bubbles at the interface between the substrate 21 and the liquid metal 22 can improve the wettability of the substrate 21 by the liquid metal 22. This effect is due to the interaction of the cavitation bubbles in contact with or in the vicinity of the surface of the substrate 21, in particular the implosion of the cavitation bubbles. This reduces the surface tension at the interface between the substrate 21 and the liquid metal 22. This increases the wettability of the surface of the substrate 21 by the liquid metal 22. In addition, when the substrate has an oxide layer, it is noted that the cavitation formed at the interface between the substrate and the liquid metal can reduce or eliminate the oxide layer, thereby facilitating a direct connection between the substrate 21 and the liquid metal 22. Was observed. When the frequency of the ultrasonic power wave 11 decreases, the impact of cavitation bubbles on the substrate forms a cavity 27 on the surface of the substrate under the influence of local dissolution of the substrate. Cavity 27 may have a depth of tens of microns or hundreds of microns from the surface of the substrate. The formation of such cavities can worsen the surface condition of the substrate.

As a result of the increase in the wettability of the surface of the substrate 21 by the liquid metal 22, a liquid metal layer 25 called a coating layer is formed on the substrate. When removing the substrate 21 from the liquid metal plating bath, the coating layer 25 remains around the substrate 21. The coating layer is cooled and solidified to form a durable solid deposit over time.

The frequency of the ultrasonic waves known as power waves is preferably 10 kHz to 250 kHz, preferably 10 to 100 kHz. The higher the frequency, the lower the effect of cavitation bubbles on the substrate surface, which is believed to reduce the formation of the cavity 27. This is because the size of the cavitation bubble decreases as the frequency increases. Preferably, the frequency of the ultrasonic power wave 11 is adjusted to limit or even prevent the appearance of such cavities in order to preserve the surface state of the substrate.

Therefore, it is advantageous that the frequency of the ultrasonic wave 11 should be larger than 20 kHz, preferably larger than 40 kHz. In order to make the influence of the cavitation bubble on the substrate 21 superficial without forming a cavity, the range of 40 kHz to 80 kHz is considered to be optimal.

courte distance dans le champ de cavitation ultrasonore

basse frequence"(저주파수 초음파 캐비테이션의 필드에서의 충격파의 생성 및 단거리 집중), 2010년 4월 12일 - 16일, 리옹, 제10회 프랑스 음향 학회(French acoustics conference)에 설명되어 있다. 하이퍼 캐비테이션 콘(hyper-cavitation cone)이라 불리는 원추부 내부에서, 캐비테이션 버블의 체적 밀도는 원추부 외부에 있는 인클로저의 나머지에서의 체적 밀도보다 더 높다. 이러한 캐비테이션 버블은 본질적으로 경계면(13)에 존재하는 캐비테이션 핵(cavitation nuclei) 때문이다.As shown in FIGS. 1A-1D, the ultrasonic waves 11 emitted by the generator 10 propagate towards the enclosure 20 and extend into contact with the liquid metal 22, a surface 13 called a boundary surface. Ultrasonic propagation 11 propagates so as to pass through and reach the liquid metal 22 through this surface. In the example shown in FIGS. 1A and 1C, the ultrasonic wave 11 is propagated to the liquid metal 22 by a waveguide 12 disposed so that the proximal end contacts the generator and the distal end is immersed into the liquid metal 22. In this case, the interface 13 corresponds to the distal end of the waveguide 12 extending perpendicular to the propagation direction of the ultrasonic wave 11. In the example shown in FIGS. 1B and 1D, the interface 13 is a wall of the enclosure 20 extending in contact with the liquid metal and disposed between the power generator 10 and the liquid metal. In general, the interface 13 is a surface in contact with the liquid metal 22 and in which the ultrasonic power wave 11 propagates. This may be a solid wall, in this case the wall of the waveguide or the wall of the enclosure. When the power of the ultrasonic wave 11 is too high, the cavitation bubble can be organized near the interface 13 to form a conical volume 15, the base of which is trimmed as a function of distance to the interface. The formation of such cavitation bubbles inside the cone is described, for example, in Dubus "Generation d'ondes de chocs et focalisation".

courte distance dans le champ de cavitation ultrasonore

basse frequence "(generation of shock waves and short-range concentrations in the field of low-frequency ultrasonic cavitation), April 12-16, Lyon, 10th French acoustics conference. Hyper cavitation cone Inside the cone, called the hyper-cavitation cone, the volume density of the cavitation bubble is higher than the volume density at the rest of the enclosure outside the cone, which is essentially the cavitation nucleus present at the interface 13. (cavitation nuclei).

Since the surface condition of the substrate may be deteriorated, it is desirable to prevent excessive exposure of the substrate 21 to high density cavitation bubbles in the hyper cavitation cone 15. For this reason, the substrate 21 is preferably disposed at a sufficient distance from the interface 13 and, if there is one, outside the hyper cavitation cone 15. Thus, the ultrasonic power wave 11 propagates at a propagation distance greater than 1 cm or even greater than 5 cm before reaching the substrate 21 in the liquid metal 22. This can prevent the substrate 21 from interacting with cavitation bubbles formed near the interface 13 or within the hyper cavitation cone 15.

1B and 1D show an embodiment in which the power ultrasound generator 10 is coupled to the waveguide 12, and the waveguide 12 extends between the ultrasound generator 10 and the enclosure 20. In this way, the waveguide is not immersed in the liquid metal 22 but transmits the ultrasonic wave 11 through the wall of the enclosure 20. According to one variant, the ultrasonic generator 10 may be disposed directly with respect to the enclosure 20 without the waveguide 12 extending between the generator and the enclosure. In this configuration, the interface 13 corresponds to the wall of the enclosure 20 in contact with the liquid metal 22 through which the ultrasonic power wave 11 propagates. FIG. 1D shows the formation of a high cavitation cone 15 extending from the interface surface 13 into the liquid metal 22.

Whatever the embodiment, the exposure period of the substrate 21 to the ultrasonic wave 11 is 1 second to several minutes, preferably 1 second to 30 seconds.

Experimental testing

The apparatus shown in FIG. 1A was used to perform an experimental test. The substrate used was first a 5XXX type aluminum alloy wire with a diameter of 1.5 to 2 mm. The liquid metal 22 consisted of tin heated to a temperature of 350 ° C. The substrate was immersed in the enclosure 20 for a period of 5 to 10 seconds. The substrate 21 was not subjected to any pretreatment such as cleaning, degreasing or pickling before being immersed in the enclosure 20. The surface of the wire included a thin layer of aluminum (aluminum oxide). During the first control test, the substrate was immersed in the enclosure and then removed without being exposed to ultrasound. 2a shows a portion of a wire in the transverse direction, ie a cross section. Tin was not wetted to the substrate, and when the substrate was removed from the enclosure, no tin deposit remained on the surface of the substrate.

Then, a second test was performed, during which 1.5 mm diameter 5XXX aluminum wire was immersed in the liquid tin plating bath. Experimental parameters are as follows.

Waveguide: Titanium TA6V-Length 375 mm-Diameter 30 mm

Ultrasonic Frequency: 20 kHz

Distance between waveguide and substrate: 10 cm

After exposure to the ultrasonic wave 11, the substrate 21 was removed from the liquid metal and then cooled.

2b shows an optical microscope observation of the cross section of the substrate in the transverse direction. Tin layers 25 forming deposits around the substrate 21 can be distinguished. FIG. 2C shows the detail of FIG. 2B. This shows that the tin layer 25 extends around the substrate 21, with a thickness of 5 to 30 μm.

2D shows a cross section (or longitudinal cross section) of the substrate 21 along the longitudinal direction. FIG. 2E shows the detail of FIG. 2D. This shows that the tin layer 25 extends along the entire length of the field of observation, with a thickness of 5 to 30 μm.

In a third test, the substrate used was a 2.5 mm thick aluminum slab. The formation of a tin layer on the aluminum slab was also observed and the thickness of the tin layer was 10 to 50 μm.

3A shows scanning electron microscopy using a field effect X-ray source for a cross section of a 1XXX diameter 1XXX aluminum alloy wire in the transverse direction. The wire was immersed in a plating bath of liquid tin heated to 260 ° C., according to the embodiment shown in FIG. 1A, and exposed to ultrasonic waves 11 at a frequency of 20 kHz. The ultrasonic power was 100 W. Tin layer 25 attached around the substrate 21 can be observed. In FIG. 3A, the region of interest A is indicated, which is the object of FIG. 3B. In this region of interest, four analysis points were identified, for which X-ray fluorescence spectral analysis was performed. 3C, 3D, 3E and 3F are spectra corresponding to analysis points A1, A2, A3 and A4 respectively shown in FIG. 3B. In each spectrum, the energy corresponding to the searched element is identified by a vertical bar. 3C corresponds to a tin coating layer 25, which confirms that the coating layer is formed by a liquid metal, in this case tin. 3d corresponds to point A2 at a deep position in the substrate 21. The spectrum representing the aluminum alloy is obtained. 3E corresponds to point A3 and shows the presence of aluminum oxide. At point A3, it can be seen that the coating layer 25 does not directly wet the substrate 21, but appears to directly wet the residual oxide layer 26. 3F corresponds to point A4 located at the interface between the substrate 21 and the coating layer 25. The spectrum reflects the dominant aluminum content with some tin. At this point, the oxide layer has been removed and the liquid metal 22 directly wets the substrate 21. Cavitation appears to have the effect of gradually reducing or removing oxide layer 26 extending around the substrate. When the oxide layer is removed by cavitation (point A4), direct adhesion of the coating layer 25 to the substrate 21 is obtained. If the oxide layer cannot be completely removed by cavitation (point A3), the oxide layer 26 remains between the coating layer 25 and the substrate 21, and the electrical continuity between the substrate 21 and the coating layer 25 none. This electrical continuity is particularly sought in the case of attachments, for example for application in electrical connection applications. Thus, for this type of application, one would like to remove the oxide layer.

4A shows scanning electron microscopy using a longitudinal field effect X-ray source of a wire processed in a manner similar to the wire described with respect to FIGS. 3A-3F while increasing the power of the applied ultrasound 11. . The tin coating layer 25 attached around the substrate 21 can be seen, and the thickness of the layer is about 10 mu m. It can be seen that the coating layer 25 penetrates locally inside the substrate in the cavity 27, which may be deeper than 100 microns or 200 microns. In this way, the liquid metal 22 penetrates locally into the substrate 21, and the cavity 27 forms open pores. FIG. 4A defines the range of the region of interest B corresponding to the cavity 27 and forming the object of FIG. 4B. In this region of interest, four analysis points were identified, where X-ray fluorescence spectroscopy was performed. 4C, 4D, 4E and 4F are spectra corresponding to analysis points B1, B2, B3 and B4 respectively shown in FIG. 4B. Point B1 (FIG. 4C) corresponds to a local aluminum residue. This residue is embedded in a cavity 27 200 microns deep, which is filled with tin. Point B2 (FIG. 4D) indicates the inclusion of copper in the substrate. Point B3 (FIG. 4E) corresponds to the substrate material, in this case an aluminum alloy. With regard to the point B4 (FIG. 4F), this represents the material in the cavity 27, in this case tin.

FIG. 5A shows a scanning electron microscopy using a longitudinal field effect X-ray source of a substrate 21 in the form of a 2.5 mm thick aluminum sheet processed in a similar manner to the wire described in connection with FIGS. 4A-4F. . Tin coating layers 25 formed on both sides of the substrate 21 can be observed. Cavity 27 is also visible. Two regions of interest C and D are shown in FIG. 5A, which are the objects of FIGS. 5B and 5C. The region of interest C corresponds to the cavity 27 extending from the surface of the sheet to a depth of approximately 250 μm. 5A, 5B and 5C are X-ray fluorescence spectra corresponding to analysis points C1, C2 and C3 shown in FIG. 5B. Point C1 (FIG. 5D) corresponds to substrate material 21, in this case an aluminum alloy. Point C2 (FIG. 5E) shows the material filling the cavity 27, in this case tin. Point C3 (FIG. 5F) corresponds to the interface between substrate 21 and cavity 27 with dominant aluminum and some tin. Therefore, tin in the cavity 27 directly wets aluminum.

5G and 5H are X-ray fluorescence spectra corresponding to analysis points D1 and D2 shown in FIG. 5C. This analysis point is located at the interface between the substrate 21 and the tin coating layer 25. At point D1 (FIG. 5G), some aluminum oxide remaining (high amplitude oxygen peak) is observed, while at point D2 (FIG. 5H) the spectrum represents an aluminum alloy. At this point the oxide layer was removed, which caused the substrate to be directly wetted by tin.

Experimental tests show that the coating layer 25 is formed after partial or complete destruction of the oxide layer 26 by cavitation bubbles. As the power increases (or decreases in frequency) a cavity 27 is formed on the surface of the substrate. Such a cavity may be greater than 50 μm in depth and greater than 200 μm in depth. Such a cavity can cause deterioration of the surface state of the substrate 21.

In the previous example, the substrate 21 is metallic and made of metal. The test was successfully performed on a substrate made of the first nonmetallic material. The table below summarizes the different configurations tested.

First material (substrate) Liquid metal aluminum Remark SiAlON ceramic Remark titanium Remark SiAlON ceramic Remark steel aluminum SiAlON ceramic aluminum Alumina aluminum steel aluminum titanium aluminum Graphite aluminum

Table 1: Configurations Tested for First Application Example

SiAlON ceramics referenced in Table 1 are ceramics known to those skilled in the art and are denoted by the term silicon aluminum oxynitride.

If the liquid metal is aluminum, it may advantageously contain a concentration of magnesium at a concentration of 20 ppm or greater than 0.05% or even greater than 0.5% or 0.7% but less than 1%. This reduces the cavitation threshold of liquid aluminum. One target application is to plate a metal, for example steel, with aluminum.

The method tested in the previously described experimental test can be used industrially, for example using a device such as shown in FIGS. 6A and 6B. 6A shows an apparatus that includes a take-up reel 51 and a take-up reel 52. The wire 21 is unwound from the unwinding reel 51 and wound around the winding reel 52 after passing through a plating bath containing the liquid metal 22 in the enclosure 20. The movement of the wire is indicated by the horizontal arrow. The freewheel 53 is used to adjust the trajectory of the wire. The plating bath of the liquid metal 22 receives ultrasonic sound waves 11 generated by the generator 10 arranged below the bottom of the enclosure 20, and the waveguide 12 has its respective power generator 10 and the enclosure 20. Extends between the bottoms. The movement time of the wire part in the plating bath is adjusted according to the driving speed, and may be 1 second or more, preferably 1 second to 1 minute, more preferably 10 seconds to 1 minute. During exposure to the ultrasonic wave 11, the liquid metal is attached around the wire in the form of a coating layer 25. As the wire exits the liquid plating bath, the coating layer 25 solidifies to form a deposit. FIG. 6B shows a variant of FIG. 6A. Ultrasound is generated by the generator 10 coupled to the waveguide 12, which is submerged into the liquid metal 22. The acoustic wave 11 is propagated by a tubular shape auxiliary waveguide 12 'which can be modified to propagate the acoustic wave 12' in the liquid metal 22.

Forming the coating layer 25 on the surface of the solid substrate 21

-Anti-corrosion protection;

Formation of a conductive layer;

Welding aids by local melting of the coating layer in tack welds

It may have an application such as.

According to one variant, the substrate may successively go through two successive plating baths, the first plating bath for forming the first thin coating layer, and the second plating bath for increasing the thickness of the coating layer.

According to a second application, the invention can be used to increase the wettability of the solid substrate 21 lying at the interface between the ultrasonic generator control device 30 and the liquid metal 22. The solid substrate 21 is then immersed in the liquid metal 22 by confining a portion of the wall 20p of the enclosure 20 including the liquid metal 22 (FIG. 7A), or the ultrasonic control device 30. Is part of the containment system 35 (FIG. 7C). Increased wettability of the liquid metal 22, as described above, is not used to form a coating layer on the substrate, but is used to improve the transmission characteristics of the control ultrasound 31 intended for nondestructive testing in the enclosure. do.

7a shows a fast neutron reactor vessel 20 in which coolant is formed by liquid metal 22, in particular liquid sodium or liquid lead. Unlike water used in pressurized water reactors, liquid sodium is optically opaque. Thus, the use of acoustic waves is useful for continuous monitoring of work or during maintenance work. There are many applications such as "visualization" in opaque media, distance measurement, surface metrology, detection of defects or cracks. A notable limitation is the high temperature at which the coolant is to be maintained in the liquid state, which varies from 200 ° C. for maintenance work to 550 ° C. when the reactor is in operation. The ultrasonic control device 30 is used to emit the ultrasonic control wave 31 and may also serve as a detector to measure the time between the emission of the ultrasonic control wave and the detection of the reflected ultrasonic waves. The ultrasonic control wave 31 propagates, for example, 10 times lower than the surface power density of the power ultrasonic wave 11. The frequency of the ultrasonic control wave 31 is greater than the frequency of the ultrasonic power wave 11. The frequency is typically 1 MHz to 100 MHz. The power density of the ultrasonic control waves in the liquid metal is below the cavitation threshold.

The ultrasonic control device 30 may be disposed outside the container with respect to the container so as to propagate the ultrasonic control wave 31 through the wall 20p of the container. At this time, the container forms an enclosure 20, through which the ultrasonic waves 31 propagate between the ultrasonic control device 30 and the liquid metal 22. The surface of the enclosure in contact with the liquid metal and in which the ultrasonic control wave 31 propagates forms the so-called coupling surface 23. In order to optimize the transmission of the ultrasonic control wave 31 through the coupling surface 23, the wettability of the liquid metal 22 on the coupling surface, as described above, is coupled to the ultrasonic power wave 11. 23) can be improved by exposing. This facilitates the transmission of the ultrasonic control wave 31 through the wall 20p of the vessel. Thus, the coupling surface 23 is exposed to the power ultrasound 11 emitted by the power ultrasound generator 10. As can be seen in FIG. 7B, the coupling surface 23 defines a solid substrate 21 made of a metal forming the wall 20p of the vessel 20 in the vicinity of the coupling surface. Application of the power ultrasound 11 increases the wettability of the surface of the substrate 21 by the liquid metal 22 and promotes the transmission of the ultrasound control wave 31 through the coupling surface 23. It can also facilitate the transmission of reflected ultrasound 32, which propagates from the vessel to the ultrasound control device 30 through the coupling surface.

The power generator 10 is provided such that the ultrasonic power wave 11 at the coupling surface 23 has a power density greater than the cavitation threshold of the liquid metal 22. The frequency of the ultrasonic power wave 11 is preferably 10 kHz to 250 kHz. In order to prevent the formation of cavities in the vessel, under the influence of cavitation bubbles, the frequency of the power ultrasound 11 is advantageously greater than 40 kHz, typically 40 kHz to 80 KHz. The power generator 10 may be provided outside the container 20 or inside the container. Preferably, the ultrasonic power wave 11 propagates in a liquid metal 22 at a propagation distance greater than 1 cm, preferably greater than 5 cm, before reaching the coupling surface 23. The latter forms the surface 21s of the substrate. This prevents the coupling surface 23 from being exposed to too high a density of cavitation bubbles, as described in connection with the first application.

According to a variant shown in FIG. 7C, the ultrasonic control device 30 is immersed in the vessel 20 and confined in a containment system 35 formed of containment metal. As can be seen in FIG. 7D, the containment system 35 then forms a coupling surface 33 extending in contact with the liquid metal, through which the control wave 31 passes from the ultrasonic control device 30. Propagates to the liquid metal 22. The coupling surface 33 delimits the solid substrate 21 made of the metal that forms the containment system 35. Application of the ultrasonic power wave 11 increases the wettability of the liquid metal 22 in the metal of the containment system 35 and facilitates the transmission of the ultrasonic control wave 31 through the coupling surface 33. This may also facilitate the transmission of reflected ultrasound 32 propagated from the vessel to the ultrasound control device 30. The power generator 10 is provided such that the ultrasonic power wave 11 has a power density greater than the cavitation threshold of the liquid metal at the coupling surface 23. The frequency of the ultrasonic power wave 11 is preferably 10 kHz to 250 kHz. Frequencies lower than 40 KHz, for example 20 kHz, can cause the formation of cavities in the containment system 35 at the level of the coupling surface 33. This is not important because the containment system 35 can be exchanged.

The configuration shown in Table 2 can be implemented as part of this application.

First material (substrate) Liquid metal titanium salt steel salt Stainless steel salt ceramic salt

Table 2: Example of Configuration Related to Second Embodiment

The ceramic may be, for example, a ceramic based on silicon, aluminum, nitrogen or oxygen, such as silicon aluminum oxynitride (SiAlON), silicon nitride (Si 3 N 4) or ruby.

Claims (16)

In the method of processing the solid substrate 21,
a) bringing the solid substrate (21) into contact with a liquid metal (22) confined within an enclosure;
b) propagating an ultrasonic wave, called a power wave 11, emitted by a power ultrasound generation device 10 in the liquid metal 22, the surface of the solid substrate In the ultrasonic power wave 11 so that the power density of the ultrasonic power wave 11 is greater than the cavitation threshold of the liquid metal, before the ultrasonic power wave reaches the surface 21s of the solid substrate 21. Propagating through metal (22), wherein the frequency of the ultrasonic power wave is between 10 kHz and 250 kHz;
c) after propagation of the ultrasonic power wave 11, obtaining a cavitation bubble 22 in the liquid metal, the cavitation bubble reaching the surface 21s of the solid substrate 21 and , The interaction of the surface 21s of the solid substrate 21 with the cavitation bubble increases the wettability of the surface 21s by the liquid metal 22.
Method comprising a. A method according to claim 1, wherein the frequency of the ultrasonic power wave (11) is greater than 40 kHz. The acoustic power wave (11) of claim 1 or 2, wherein during step b) an acoustic power wave (11) is greater than 1 cm in the liquid metal (22) inside the enclosure (20). Preferably propagating with a propagation distance of greater than 5 cm. The method according to any one of claims 1 to 3,
The ultrasonic power wave 11 can in particular propagate from the power ultrasonic generator 10 and pass through a so-called boundary surface 13 which extends in contact with the liquid metal 22,
The method includes the steps of forming a cavitation bubble inside a cone 15 called a hyper-cavitation cone,
The density of the cavitation bubble is greater than outside of the cone, the hyper cavitation cone 15 extends from the interface 13 into the liquid metal 22,
The method is characterized in that in step c) the solid substrate (21) is provided outside the hyper cavitation cone. 5. The method according to claim 4, wherein the interface (13) is a solid wall, wherein the ultrasonic power wave propagates through the solid wall. The method according to any one of claims 1 to 5, wherein the solid substrate 21 is a metal substrate or a ceramic substrate,
d) exposing the solid substrate 21 to the ultrasonic power wave 11 during an exposure period of preferably 1 second to 1 minute, wherein the liquid metal 22 is coated on the solid substrate with a coating layer 25. Forming a layer known as;
e) removing the substrate from the enclosure;
f) after said removal, solidifying said liquid metal to form a deposit 25 on said solid substrate
Method further comprising a. 7. The method according to claim 6, wherein the solid substrate (21) is metallic and the metal constituting the solid substrate has a melting temperature strictly greater than the melting temperature of the liquid metal (22). Method according to claim 6 or 7, characterized in that the liquid metal (22) is an electrically conductive metal such that the deposit (25) formed in step f) is an electrically conductive deposit. The method of claim 8, wherein the liquid metal contains tin, zinc or lead. 10. The method according to claim 6, wherein the thickness of the deposit formed in step f) is between 5 μm and 2 mm. 11. 6. The method according to claim 1, wherein the liquid metal comprises aluminum. 7. 12. The method of claim 11, wherein the liquid metal (22) contains less than 1% mass fraction of magnesium. The method according to any one of claims 1 to 5,
An ultrasonic wave 31, called a control wave, is propagated by the ultrasonic control device 30 in the liquid metal 22 via a surface known as a coupling surface 23, 33. The surface is the surface of the solid substrate 21 extending in contact with the liquid metal 22,
The solid substrate 21 is delimited by the coupling surfaces 23, 33,
During step c), in the liquid metal 22, the solid substrate by the liquid metal 22 to improve the transmission of the ultrasonic control wave 31 through the coupling surfaces 23, 33. 21) The wettability of the surface of 21) is increased. 14. The ultrasonic control device (30) according to claim 13, wherein the ultrasonic control device (30) is arranged outside the enclosure (20), and the coupling surface (23) is provided with the enclosure (20) and the ultrasonic control wave (31) propagated. Corresponding to an interface between liquid metals (22), wherein said solid substrate (21) is formed by a portion of said enclosure delimited by said coupling surface (23). 15. The ultrasonic control device (30) according to claim 13, wherein the ultrasonic control device (30) can be enclosed in a containment system (35), the containment system being immersed in the liquid metal (22), and the coupling surface (33) being controlled by the ultrasonic control system. Of the containment system 35 corresponding to the interface of the liquid metal 22 and the containment system 35 through which waves are propagated, the solid substrate 21 being delimited by the coupling surface 33. Formed by some. The method according to any one of claims 12 to 15, wherein the enclosure (20) is a reactor vessel and the liquid metal contains sodium or lead.

Images